Detection and multi-wavelength characterisation of galaxy clusters, groups and protocluster cores up to z=3.7

Galaxies in the Universe are distributed across an interconnected structure known as the cosmic web, formed through gravitational collapse, accretion, and merging. Within this framework, galaxy clusters and groups emerge as key environments where galaxies evolve under the combined influence of internal and environmental processes. This Thesis focuses on the detection, multi-wavelength characterisation, and scientific analysis of these systems, with particular emphasis on deep, small-area surveys capable of probing the high-redshift Universe. In this work, we employed the Adaptive Matched Identifier of Clustered Objects (AMICO) algorithm, here enhanced for application to deep, multi-band photometric data. Through careful data preparation, noise modelling, and masking strategies, we created two robust catalogues of galaxy clusters and groups up to high redshift. The AMICO-COSMOS catalogue comprises 1269 detections up to z=2, complemented by X-ray characterisation that enabled the calibration of scaling relations between optical and X-ray mass proxies. The highest-redshift application of AMICO to date produced the COSMOS-Web catalogue—the largest deep sample of galaxy groups and protocluster cores produced to date, extending to z=3.7. Among these, over 300 new high-redshift systems were identified, including several extended protocluster regions such as the AmicOne candidate, the largest among them. Leveraging these catalogues, this Thesis explores the evolution of the quiescent galaxy fraction and the red sequence over around 12 Gyr, revealing evidence of mature galaxy populations already at early cosmic times. The analysis of Brightest Group Galaxies (BGGs) uncovered systems undergoing transformation and rapid molecular gas depletion, indicative of quenching processes in action. Together, these results lay the groundwork for future studies of structure formation and galaxy evolution, particularly in view of forthcoming data from facilities such as Euclid, JWST, LSST, and Roman.